Our program proposes to design and synthesize compounds that inhibit the action of HIV Integrase. At present, integrase is the only HIV enzyme for which clinically useful inhibitors are not available. Given the recent success of combined therapy targeting reverse transcriptase and protease simultaneously, it is highly desirable to include the third target HIV integrase. We propose to carry out a coordinated series of experiment to develop such inhibitors. Our group brings unique expertise and background data to this effort. We have improved the resolution of the structure of the integrase catalytic domain substantially, providing a point of departure for structure-guided design of inhibitors. Using assays based on preintegration complexes isolated from HIV infected cells, we have identified particularly potent integrase inhibitors. We are presently attempting to form various co- crystal complexes of these inhibitors bound to the integrase catalytic domain. We plan to use integrase-inhibitor structures to design improved inhibitors, which will then be tested . Effective new inhibitors will then be analyzed as co-crystals with the integrase catalytic domain. We hope that several cycles of synthesis testing, co-crystallization and new inhibitor design will yield clinically useful drugs. While this structure-guided design strategy forms the center of our effort, we have also prepared other routes to the achievement of the goal of creating useful inhibitors. We use the unliganded integrase structure to "discover and grow" compounds that bind the active site. Such molecules will be synthesized and tested. The structures of lead drugs will identify related compounds to synthesize and test. Natural products with structures related to known inhibitors will be tested for inhibition of integrase. Finally, integrase variants insensitive to drugs will be isolated by genetic means. The locations of such changes in the integrase structure will provide information on likely locations of drug binding sites. This information will be incorporated into the design of improved small molecule inhibitors.